The present invention relates to fuel properties estimating apparatus and process for an internal combustion engine.
A vehicle known as flexible fuel vehicle (FFV) can run on a blend fuel of alcohol and gasoline as well as on gasoline.
An engine system as shown in a Published Japanese Patent Application Publication No. H06(1993)-229340 (pages. 1˜3, and FIGS. 1 and 2) is provided with an alcohol concentration sensor for sensing an alcohol concentration in fuel, and arranged to actuate a fuel pump before a start of the engine if fresh fuel is supplied to a fuel tank, to make the alcohol concentration uniform and thereby to provide satisfactory engine performance.
Since the alcohol concentration sensor is costly, there is a method for estimating an alcohol concentration of fuel in accordance with an output signal of an air fuel ratio sensor for sensing an exhaust air fuel ratio of the engine.